Emitter structure, gas ion source and focused ion beam system

ABSTRACT

There is provided an emitter structure, a gas ion source including the emitter structure, and a focused ion beam system including the gas ion source. The emitter structure includes a pair of conductive pins which are fixed to a base member, a filament which is connected between the pair of conductive pins, and an emitter which is connected to the filament and has a sharp tip. A supporting member is fixed to the base material, and the emitter is connected to the supporting member.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims priority from Japanese Patent Application No.2013-063707, filed on Mar. 26, 2013, the entire subject matter of whichis incorporated herein by reference.

TECHNICAL FIELD

The present invention relates to an emitter structure, a gas ion sourceand a focused ion beam system.

BACKGROUND

There has been known a focused ion beam system as a system forperforming observation, various evaluation or analysis, or the like on asample such as a semiconductor device, and for preparing a TEM sample bytaking a fine and thin sample fragment from a sample and fixing the thinsample fragment to a sample holder.

This focused ion beam system includes an ion source for generating ions,and radiates ions generated in the ion source as a focused ion beam.

There are many types of ion sources. For example, a plasma type ionsource and a liquid-metal ion source have been known. Recently, therehave been provided a gas field ion source (GFIS) capable of generatingfocused ion beams having a smaller beam diameter and higher luminance ascompared to the above-described ion sources.

The gas field ion source mainly includes an emitter structure having anaciculate emitter with a tip which is sharpened at an atomic level, agas source for supplying a gas such as helium (He) to the vicinity ofthe emitter, a cooling unit for cooling the emitter, and an extractionelectrode disposed at a position apart from the tip of the emitter.

Here, an emitter structure disclosed in JP-A-2012-098293 will bedescribed briefly.

As shown in FIG. 8, a emitter structure 100 mainly includes a basemember 101, a pair of conductive pins 102 fixed to the base member 101,a filament 103 connected between the tips of the conductive pins 102,and the emitter 104 connected to the filament 103.

The emitter 104 is hung and held on the filament 103 in a state where abase end portion of the emitter 104 is connected to the filament 103 byspot welding or the like.

In this configuration, after the gas is supplied to the vicinity of theemitter 104, if an extraction voltage is applied between the emitter 104and an extraction electrode (not shown) while the emitter 104 is cooled,the gas is ionized into gas ions by a high electric field formed arounda tip portion of the emitter 104. Then, the gas ions are drawn towardthe extraction electrode repulsively from the emitter 104 having apositive potential. Thereafter, the drawn gas ions are focused whilebeing appropriately accelerated, thereby becoming a focused ion beam.

Especially, since the focused ion beam generated from the gas field ionsource has a small beam diameter and narrow energy spread (radiationangle distribution), it is possible to irradiate a sample with the beamhaving a small beam diameter. Therefore, it becomes possible to improvethe resolution during observation or perform finer etching.

Meanwhile, when a crystal structure of the emitter 104 is broken, bysupplying electric power from a current source (not shown) to theemitter 104 through the conductive pins 102 and the filament 103 to heatthe emitter 104, atoms configuring the emitter 104 are rearranged.

As described above, in the emitter structure 100, since the emitter 104is held only by the filament 103, transfer of heat to the emitter 104 isperformed mainly through the filament 103. In this case, during heatingof the emitter 104, or during rearranging of the emitter 104, since theamount of heat radiation from the emitter 104 is small, the emitter 104is efficiently heated through the filament 103. However, there is aproblem in that cooling efficiency is low during cooling of the emitter104, such as during generating of gas ions.

The ion emission amount of the gas field ion source depends highly ontemperature. Thus, it is preferable to operate the gas field ion sourceat lower temperature.

Also, in the emitter structure 100, since the emitter 104 is held onlyby the filament 103 as described above, it is difficult to hold theemitter 104 perpendicularly with respect to the base member 101. Since afocused ion beam which is generated from the gas field ion source has anarrow radiation angle distribution as described above, in order tosurely radiate the focused ion beam toward a sample, the optical axis ofthe focused ion beam is required to be aligned with a desired direction.

With respect to this, JP-A-2012-098293 discloses a configurationprovided with a gimbal mechanism (tip manipulator) for adjusting thetilt or position of the optical axis of a focused ion beam generatedfrom the emitter 104.

However, the provision of the gimbal mechanism causes problems such asan increase in the number of components, and complication of the system.

SUMMARY

The present invention has been made in view of the above-describedcircumstances, and an object of the present invention is to provide anemitter structure, a gas ion source and a focused ion beam system whichare capable of improving the cooling efficiency of an emitter, reducingthe number of components, simplifying the system, and accurately andstably holding the emitter with respect to a base member.

According to an illustrative embodiment of the present invention, thereis provided an emitter structure comprising: a pair of conductive pinswhich are fixed to a base member; a filament which is connected betweenthe pair of conductive pins; and an emitter which is connected to thefilament and has a sharp tip, wherein a supporting member is fixed tothe base material, and the emitter is connected to the supportingmember.

According to this configuration, since the emitter is connected not onlyto the filament but also to the supporting member, it is possible tomore stably hold the emitter with respect to the base member, ascompared to a configuration in which the emitter is hung and held onlyby the filament as in the related-art configuration. In this case, itbecomes easy to vertically hold the emitter, and it is possible to makeit easy to align the optical axis of the focused ion beam with a desireddirection. Also, unlike in the related-art configuration, since it isunnecessary to separately provide a gimbal mechanism or the like foradjusting the tilt or position of the optical axis of the focused ionbeam, it is possible to reduce the number of components, simplify thesystem, and more accurately and stably hold the emitter with respect tothe base member.

Also, during cooling of the emitter, heat of the emitter is radiated tothe base member and so on through the supporting member. Therefore, ascompared to a case where heat of the emitter is radiated only throughthe filament as in the related-art configuration, it is possible toimprove the cooling efficiency of the emitter.

In the above emitter structure, the supporting member may be formed of amaterial having thermal conductivity higher than that of the filament.

According to this configuration, since the supporting member is formedof a material having thermal conductivity higher than that of thefilament, heat of the emitter is efficiently radiated to the supportingmember. Therefore, it is possible to surely improve the coolingefficiency of the emitter.

In the above emitter structure, the supporting member may be formedthicker than the filament.

According to this configuration, since the supporting member is formedthicker than the filament, heat of the emitter is efficiently radiatedto the supporting member. Therefore, it is possible to surely improvethe cooling efficiency of the emitter.

In the above emitter structure, the supporting member may be formed in acylindrical shape, and the emitter may be fixed while a base end portionof the emitter is inserted into the supporting member.

According to this configuration, since the emitter is inserted into thecylindrical supporting member, and is fixed in that state, it ispossible to more stably hold the emitter.

According to another illustrative embodiment of the present invention,there is provided a gas ion source comprising: the above-describedemitter structure; a gas source which is configured to supply a gas to avicinity of the emitter; a cooling unit configured to cool the emitter;an extraction electrode which is disposed apart from the tip of theemitter; and an extraction power source unit which is configured toapply an extraction voltage between the emitter and the extractionelectrode to ionize the gas into gas ions at the tip of the emitter andextract the gas ions toward the extraction electrode.

According to a further illustrative embodiment of the present invention,there is provided a focused ion beam system comprising: theabove-described gas ion source; and a beam optical system which isconfigured to convert the extracted gas ions into a focused ion beam andirradiate a sample with the focused ion beam.

According to this configuration, since the emitter structure isprovided, it is possible to stably generate gas ions, and it is possibleto continuously radiate a focused ion beam with a small beam diameterand high luminance, in a desired direction.

According to this configuration, it is possible to improve the coolingefficiency of the emitter, reduce the number of components, simplify thesystem, accurately and stably hold the emitter with respect to the basemember, and make it easy to align the optical axis of a focused ion beamwith a desired direction.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other aspects of the present invention will become moreapparent and more readily appreciated from the following description ofillustrative embodiments of the present invention taken in conjunctionwith the attached drawings, in which:

FIG. 1 is a view illustrating the overall configuration of a focused ionbeam system according to a first illustrative embodiment of the presentinvention;

FIG. 2 is a view illustrating the configuration of a focused ion beamlens barrel included in the focused ion beam system;

FIG. 3 is a perspective view of an emitter structure;

FIG. 4 is a cross-sectional view taken along a line IV-IV of FIG. 3;

FIG. 5 is an enlarged view of a tip of an emitter;

FIG. 6 is an enlarged view of the tip of the emitter at an atomic level;

FIG. 7 is a view illustrating a state where gas ions are generated fromthe tip of the emitter; and

FIG. 8 is a perspective view of a related-art emitter structure.

DETAILED DESCRIPTION

Hereinafter, illustrative embodiments of the present invention will bedescribed with reference to the accompanying drawings.

Focused Ion Beam System

FIG. 1 is a view illustrating the overall configuration of a focused ionbeam system 1.

As shown in FIG. 1, the focused ion beam system 1 of the presentillustrative embodiment mainly includes a stage 2 on which a sample S isplaced, a focused ion beam lens barrel 3 which radiates a focused ionbeam (FIB), a detector 4 which detects secondary charged particles Rgenerated by irradiation with the focused ion beam (FIB), a gas gun 5which supplies a source gas G1 for forming a deposition film, and acontrol unit 7 which generates image data based on the detectedsecondary charged particles R and controls a display unit 6 to displaythe image data.

The stage 2 is configured to operate based on instructions of thecontrol unit 7, and is supported by a displacing mechanism 8 capable ofdisplace the stage 2 on five axes. Specifically, the displacingmechanism 8 includes a horizontal movement mechanism 8 a which movesalong an X axis and a Y axis which are parallel to a horizontal planeand are perpendicular to each other and along a Z axis which isperpendicular to the X axis and the Y axis, a tilt mechanism 8 b whichrotates the stage 2 around the X axis (or the Y axis), thereby tiltingthe stage 2, and a rotation mechanism 8 c which rotates the stage 2around the Z axis.

Therefore, it is possible to radiate the focused ion beam (FIB) toward adesired position using the displacing mechanism 8 to displace the stage2 on the five axes. Meanwhile, the stage 2 and the displacing mechanism8 are accommodated inside a vacuum chamber 9. Therefore, irradiationwith the focused ion beam (FIB), supply of the source gas G1, and thelike are performed inside the vacuum chamber 9.

Focused Ion Beam Lens Barrel

FIG. 2 is a view illustrating the configuration of the focused ion beamlens barrel 3.

As shown in FIG. 2, the focused ion beam lens barrel 3 includes a gasfield ion source (a gas ion source) 21 for generating gas ions G3 (seeFIG. 7) from a gas G2, and a beam optical system 31 for converting thegas ions G3 into a focused ion beam (FIB), and radiating the focused ionbeam onto the sample S.

The gas field ion source 21 of the focused ion beam lens barrel 3 mainlyincludes an emitter structure 22, a gas source 23, a cooling unit 24, anextraction electrode 25, and an extraction power source unit 26.

FIG. 3 is a perspective view of the emitter structure 22.

As shown in FIGS. 2 and 3, the emitter structure 22 includes an emitter52 and a heating unit 53 which are accommodated in an ion generatingchamber 51, and a supporting member 54 which supports the emitter 52.

The ion generating chamber 51 is formed of, for example, a ceramicmaterial, in a box shape with an open bottom. Specifically, the iongenerating chamber 51 includes a base member 61 and a surrounding member62 which extends downward from the peripheral edge of the base member 61and surrounds the base member 61. The ion generating chamber 51 isconfigured to maintain the inside thereof in a high vacuum state.

The heating unit 53 performs a function of locally heating the tip ofthe emitter 52 to a predetermined temperature based on a current from acurrent source 63 which operates according to an instruction from thecontrol unit 7, thereby rearranging atoms configuring the emitter 52.Specifically, the heating unit 53 includes a pair of conductive pins 65,and a filament 66 which is connected between the tips of the conductivepins 65.

Each conductive pin 65 is formed of a conductive material such as ametal in a solid rod shape, and is fixed to the base member 61 bysoldering in a state where the conductive pin 65 is passing through thebase member 61. Therefore, the upper end portions of the conductive pins65 are positioned outside the ion generating chamber 51, and the lowerend portions of the conductive pins 65 are positioned inside the iongenerating chamber 51. From each conductive pin 65, a wiring line 67 isled out toward the current source 63.

The filament 66 is formed of a high-resistance material such as tungsten(W), and both end portions of the filament 66 are connected to the lowerend portions of the conductive pins 65, respectively, by welding or thelike. As shown in FIGS. 2 and 3, the filament 66 is held in a “V” shapewhich is inclined downward toward the central portion.

FIG. 4 is a cross-sectional view taken along a line IV-IV of FIG. 3.

As shown in FIGS. 3 and 4, in the present illustrative embodiment, thesupporting member 54 is formed of a material, such as copper, havingthermal conductivity higher than that of the filament 66, and formed ina cylindrical shape having a diameter thicker than the filament 66 andthe conductive pins 65. The supporting member 54 is inserted into athrough-hole 61 a formed at a portion of the base member 61 positionedbetween the conductive pins 65 as seen in a side view. In this state,the supporting member 54 is fixed to the base member 61 by soldering orthe like. Therefore, the upper end portion of the supporting member 54is positioned outside the ion generating chamber 51, and the lower endportion of the supporting member 54 is positioned inside the iongenerating chamber 51.

FIG. 5 is an enlarged view of the tip of the emitter 52.

The emitter 52 is an aciculate member having a sharp tip (lower end) asshown in FIG. 5, and is configured, for example, by coating a basematerial 52 a made of tungsten (W) or the like with a noble metal 52 bsuch as iridium (Ir). The tip of the emitter 50 is sharpened at anatomic level, and specifically, the tip is configured such that acrystal structure becomes a pyramidal shape as shown in FIG. 6. FIG. 6is an enlarged view of the tip of the emitter 52 at an atomic level.

An upper portion of the emitter 52 is connected to the central portion(lower edge portion) of the filament 66 by spot welding or the like.Also, the upper end portion (insertion portion 52 c) of the emitter 52positioned higher than the connection portion with the filament 66 isinserted into the supporting member 54 from below.

Meanwhile, at a portion of the supporting member 54 overlapping theinsertion portion 52 c of the emitter 52 in a radial direction (aportion of the supporting member 54 into which the insertion portion 52c of the emitter 52 is inserted), a through-hole 68 is formed in theradial direction, and a locking screw 69 is screwed into thethrough-hole 68. The tip portion of the locking screw 69 passes throughthe supporting member 54 in the radial direction and comes into contactwith the peripheral surface of the emitter 52 (the insertion portion 52c). Therefore, the emitter 52 is supported in the supporting member 54in a state where the insertion portion 52 c is interposed between theedge surface of the locking screw 69 and the inner circumferentialsurface of the supporting member 54.

The gas source 23 is for supplying a small amount of gas (for example,helium (He)) G2 to the vicinity of the emitter 52, and is connected tothe ion generating chamber 51 through a gas introduction pipe 23 a.

The extraction electrode 25 is provided to extend inward from the edgeof the opening of the ion generating chamber 51 and be apart from thetip (lower end) of the emitter 52. Further, an opening 25 a is formed ata position of the extraction electrode 25 facing the tip (lower end) ofthe emitter 52 in a vertical direction.

The extraction power source unit 26 is a power source for applying anextraction voltage between the extraction electrode 25 and the emitter52. The extraction power source unit 26 applies the extraction voltage,thereby ionizing the gas G2 into gas ions G3 at the tip of the emitter52 as shown in FIG. 7, and then extracting the gas ions G3 toward theextraction electrode 25.

The cooling unit 24 is for cooling the emitter 52 by a coolant such asliquid helium or liquid nitrogen. Incidentally, the present invention isnot limited thereto, the cooling unit can be configured in any otherways as long as it is possible to cool at least the emitter 52. Forexample, the cooling unit can be configured such that a cooling block, arefrigerator, or the like is used to perform cooling.

On the ion generating chamber 51, a cold head 71 for dissipating heat ofthe emitter 52 is provided. The cold head 71 is formed of a ceramicmaterial such as alumina, sapphire, or aluminum nitride in a blockshape, and is fixed to the upper surface of the base member 61. Aportion of the cold head 71 facing the supporting member 54 is formedwith an accommodating recess 72 for accommodating the upper end portionof the supporting member 54 (a protruding portion from the base member61) is formed. Then, the supporting member 54 is accommodated in thehousing recess 72 in a state where the peripheral surface of thesupporting member 54 is close to or in contact with the innercircumferential surface of the housing recess 72.

Also, at portions of the cold head 71 facing the conductive pins 65,through-holes 73 are formed through the cold head 71 in the verticaldirection, respectively. The upper end portions of the conductive pins65 are inserted into the through-holes 73 from below, and are connectedto the wiring lines 67 inside the through-holes 73.

Beam Optical System

As shown in FIG. 2, below the extraction electrode 25, a cathode 32having a ground potential is provided. An acceleration voltage from anacceleration power source unit 33 is applied between the cathode 32 andthe emitter 52, whereby energy is applied to the extracted gas ions G3.As a result, the gas ions are accelerated, thereby being converted intoan ion beam. Below the cathode 32, a first aperture 34 for narrowing theion beam is provided. Below the first aperture 34, a condenser lens 35for focusing the ion beam, thereby converting the ion beam into afocused ion beam (FIB) is provided.

Below the condenser lens 35, an aligner 36 for adjusting the opticalaxis of the focused ion beam (FIB) is provided.

Also, below the aligner 36, a second aperture 37 for further narrowingthe focused ion beam (FIB) is provided to be movable in X-axis andY-axis directions. Below the second aperture 37, a polarizer 38 forradiating the focused ion beam (FIB) onto the sample S is provided.Below the polarizer 38, an objective lens 39 for focusing the focusedion beam (FIB) on the sample S is provided.

The cathode 32, the acceleration power source unit 33, the firstaperture 34, the condenser lens 35, the aligner 36, the second aperture37, the polarizer 38, and the objective lens 39 configure the beamoptical system 31 for converting the extracted gas ions G3 into thefocused ion beam (FIB) and then irradiating the sample S with thefocused ion beam. Also, although not shown, an astigmatism corrector anda beam-position adjusting mechanism used in a related-art focused ionbeam system are also included in the beam optical system 31.

The detector 4 detects secondary charged particles R such as secondaryelectrons, secondary ions, reflected ions, and scattered ions generatedfrom the sample S during irradiation with the focused ion beam (FIB),and outputs the detection result to the control unit 7.

The gas gun 5 is configured to supply a compound gas containing amaterial (for example, phenanthrene, platinum, carbon, or tungsten) tobe a raw material for a deposition film, as the source gas G1. Thesource gas G1 is decomposed and separated into a gas component and asolid component by the secondary charged particles R generated byirradiation with the focused ion beam (FIB). Then, the solid componentof the separated two components is deposited, thereby becoming thedeposition film.

Also, for the gas gun 5, a material (for example, xenon fluoride,chlorine, iodine, or water) for selectively accelerating etching can beused. For example, in a case where the sample S is Si-based, xenonfluoride can be used, and in a case where the sample S is organic-based,water can be used. Also, it is possible to advance etching on a specificmaterial by supplying the compound gas at the same time as irradiationwith the ion beam.

The control unit 7 is configured to generally control the individualcomponents, and to be able to appropriately change the extractionvoltage, the acceleration voltage, the beam current and the like. Forthis reason, it is possible to freely adjust the beam diameter of thefocused ion beam (FIB). Therefore, it is possible not only to acquire anobservation image but also to locally perform etching (rough processing,finish processing, or the like) on the sample S.

The control unit 7 converts the secondary charged particles R detectedby the detector 4, into a luminance signal, thereby generatingobservation image data, and then controls the display unit 6 such thatthe display unit 6 outputs an observation image based on the observationimage data. Therefore, it is possible to confirm the observation imagethrough the display unit 6. The control unit 7 is connected to an inputunit 7 a which can be used for an operator to input, and controls theindividual components based on a signal input by the input unit 7 a.That is, the operator can use the input unit 7 a to irradiate a desiredarea with the focused ion beam (FIB), thereby observing the desiredarea, or to perform etching on a desired area, or to irradiate a desiredarea with the focused ion beam (FIB) while supplying the source gas G1to the desired area, thereby depositing a deposition film.

Subsequently, a case of using the focused ion beam system 1 will bedescribed below.

First, initial setting in a case of radiating the focused ion beam (FIB)according a sample S or a purpose is performed. That is, the extractionvoltage, the acceleration voltage, a gas pressure at which the gas G2will be supplied, a temperature, and the like are set to optimal values.Also, the position or inclination of the gas field ion source 21, theposition of the second aperture 37, and the like are adjusted, wherebyoptical axis adjustment is performed.

After the initial setting ends, the gas G2 is supplied from the gassource 23 into the ion generating chamber 21 while the emitter 52 iscooled to a predetermined temperature, for example, about 20 K to 100 K,by the cooling unit 24.

In this case, heat of the emitter 52 is radiated to the cold head 71mainly through the supporting member 54, and is also radiated to thecold head 71 through the supporting member 54 and the base member 61,and then is radiated to the outside through the cooling unit 24. At thistime, the heat of the emitter 52 is also radiated to the cold head 71through the heating unit 53 such as the filament 66 and the conductivepins 65. However, the amount of heat radiation through the supportingmember 54 is larger than the amount of heat radiation through theheating unit 53. Therefore, the emitter 52 is efficiently cooled.

After supply of the gas G2 and cooling of the emitter 52 aresufficiently performed, the extraction voltage is applied between theextraction electrode 25 and the emitter 52 by the extraction powersource unit 26. Then, the electric field of the tip of the emitter 50becomes locally higher, and thus the gas G2 in the ion generatingchamber 51 is ionized into gas ions G3 at the tip of the emitter 52 bythe electric field as shown in FIG. 7. Then, the gas ions G3 areextracted toward the extraction electrode 25 repulsively from theemitter 52 which is maintained at a positive potential.

The extracted gas ions G3 are converted into the focused ion beam (FIB)by the beam optical system 31, and the focused ion beam (FIB) isradiated toward the sample S as shown in FIG. 2. In this way,observation on the sample S, etching, or the like can be performed.Also, in a case of radiating the focused ion beam (FIB), it is possibleto supply the source gas G1 from the gas gun 5, thereby generating adeposition film. That is, the secondary electrons generated byirradiation with the focused ion beam (FIB) decompose the source gas G1into a gas component and a solid component and separate the gascomponent and the solid component from each other. Then, of theseparated two components, only the solid component is deposited on thesample S, thereby forming a deposition film.

As described above, besides observation or processing, generation of adeposition film is possible. Therefore, by appropriately using thesefeatures, it is possible to widely use the focused ion beam system 1 ofthe present illustrative embodiment as a microscope or an apparatus forperforming length measurement, cross-section observation, cross-sectionlength measurement, preparing of a TEM sample, mask repair, drawing, andthe like.

Especially, since the focused ion beam (FIB) of the present illustrativeembodiment is a beam generated from the gas field ion source 21, thefocused ion beam (FIB) is a beam having a smaller beam diameter andhigher luminance as compared to a plasma type ion source or aliquid-metal ion source. Therefore, in a case of performing observation,it is possible to perform observation at high resolution, and in a caseof performing processing, it is possible to perform fine and extremelyaccurate processing.

Meanwhile, in a case where the crystal structure of the emitter 52 isbroken during use, rearrangement of atoms configuring the emitter 52 isperformed. Specifically, the heating unit 53 is operated, therebylocally heating the tip of the emitter 52 (for example, at 800° C. to900 ° C. for several minutes). At this time, heating is performed basedon a heating sequence stored in a memory 7 b. As a result, the atomsconfiguring the tip of the emitter 52 are rearranged, whereby it ispossible to restore the crystal structure of the tip of the emitter 52to the original crystal structure shown in FIG. 6.

Subsequently, replacement of the emitter 52 will be described.

As shown in FIGS. 3 and 4, in a case of removing the emitter 52, first,the locking screw 69 is unscrewed, and the emitter 52 is pulled out fromthe supporting member 54. Subsequently, both end portions of thefilament 66 are removed from the conductive pins 65, and the emitter 52is removed from the filament 66.

Meanwhile, in a case of attaching a new emitter 52, first, both endportions of the filament 66 are connected to the lower end portions ofthe conductive pins 65, and an upper portion of the emitter 52 isconnected to the central portion of the filament 66 by spot welding orthe like. Thereafter, the upper portion (insertion portion 52 c) of theemitter 52 is inserted into the supporting member 54. Then, the emitter52 is fixed in the supporting member 54 by the locking screw 69.

Then, replacement of the emitter 52 ends.

As described above, in the present illustrative embodiment, the emitter52 is connected to the supporting member 54 fixed to the base member 61.

According to this configuration, since the emitter 52 is connected notonly to the filament 66 but also to the supporting member 54, it ispossible to more stably hold the emitter 52 with respect to the basemember 61, as compared to a configuration in which the emitter is hungand supported only by the filament 103 (see FIG. 8) as in therelated-art configuration. In this case, it becomes easy to verticallyhold the emitter 52 with respect to the base member 61, and it ispossible to make it easy to align the optical axis of the focused ionbeam (FIB) with a desired direction.

Also, unlike in the related-art configuration, since it is unnecessaryto separately provide a gimbal mechanism or the like for adjusting thetilt or position of the optical axis of the focused ion beam (FIB), itis possible to reduce the number of components, simplify the system, andmore accurately and stably hold the emitter 52 with respect to the basemember 61.

Further, in the present illustrative embodiment, during cooling of theemitter 52, heat of the emitter 52 is radiated to the base member 61,the cold head 71, and so on through the supporting member 54. Therefore,as compared to a case where heat of the emitter is radiated only throughthe filament 103 (see FIG. 8) as in the related-art configuration, it ispossible to improve the cooling efficiency of the emitter 52.

In this case, the supporting member 54 has thermal conductivity higherthan that of the filament 66, and is formed thicker than the filament66, heat of the emitter 52 is efficiently radiated to the supportingmember 54. Therefore, it is possible to surely improve the coolingefficiency of the emitter 52.

Further, in the present illustrative embodiment, since the emitter 52 isinserted into the cylindrical supporting member 54 and is fixed in thatstate, it is possible to more stably hold the emitter 52.

Furthermore, according to the gas field ion source 21 and the focusedion beam system 1 of the present illustrative embodiment, since theemitter structure 22 is provided, it is possible to stably generate thegas ions G3, and it is possible to continuously radiate the focused ionbeam (FIB) with a small beam diameter and high luminance in a desireddirection.

While the present invention has been shown and described with referenceto certain illustrative embodiments thereof, it will be understood bythose skilled in the art that various changes in form and details may bemade therein without departing from the spirit and scope of theinvention as defined by the appended claims.

For example, in the above-described illustrative embodiment, the crystalorientation of the emitter 52 is set to a (111) plane. However, thecrystal orientation of the emitter may be set to a (100) plane or a(110) plane.

Also, in the above-described illustrative embodiment, the base material52 a of the emitter 52 is formed of tungsten (W). However, the basematerial 52 a may be formed of molybdenum (Mo). Also, the noble metal 52b to coat the surface of the base material 52 a is iridium (Ir).However, as the noble metal 20 b, any other material such as palladium(Pd), rhodium (Rh), rhenium (Re), or osmium (Os) may be used.Especially, since the surface of the emitter 52 is coated by the noblemetal 52 b which is one of materials as described above, the emitter 52has chemical resistance. Also, in terms of chemical resistance, it ispreferable to use iridium (Ir).

Also, in the above-described illustrative embodiment, the emitter 52having a crystal structure in which one atom (an atom Al) is arranged atthe tip edge is described as an example. However, the present inventionis not necessarily limited to the case where the emitter has the tip endwith one atom. The emitter may have any other crystal structure such asa crystal structure in which three atoms are arranged at the tip edge aslong as the same crystal structure can be restored by a restoringprocess (atom rearrangement). Also, the crystal structure depends on thematerial of the crystal, and the restoring process.

Also, in the above-described illustrative embodiment, as the gas G2which is supplied into the ion generating chamber 51, helium (He) gas issupplied. However, the present invention is not limited thereto. Forexample, argon (Ar) gas, neon (Ne) gas, krypton (Kr) gas, xenon (Xe)gas, or the like may be used. Further, besides noble gases, a gas suchas hydrogen (H₂) or oxygen (O₂) can be used. In this case, according touse of the focused ion beam (FIB), the kind of gas G2 may be switched inmidstream or two or more gases G2 may be mixed and then supplied.

Also, in the above-described illustrative embodiment, in a case ofrearranging the atoms configuring the emitter 52, the tip of the emitter52 is locally heated. In this case, in addition to heating, electronsmay be emitted in a strong electric field, resulting in rearrangement.Also, in addition to heating, in a strong electric field, electrons maybe emitted while helium (He) gas, neon (Ne) gas, or argon (Ar) gas maybe introduced, resulting in rearrangement. Alternatively, in addition toheating, oxygen (O₂) or nitrogen (N₂) may be introduced, resulting inrearrangement. Even in these cases, it is possible to achieve the sameeffects.

Also, in the above-described illustrative embodiment, a configuration inwhich the conductive pins 65 and the supporting member 54 are fixed tothe base member 61 by spot welding or the like is described. However,the present invention is not limited thereto. The conductive pins 65 andthe supporting member 54 can be fixed by a variety of methods such asscrewing. For example, a supporting member 54 having a male screwportion formed at the peripheral surface may be inserted into thethrough-hole 61 a of the base member 61, and nut members may be screwedto the supporting member 54 from both sides of the base member 61 in thevertical direction. In this way, it is possible to fix the supportingmember 54 with respect to the base member 61, with the base member 61interposed between the two nut members. Also, by the same method, it ispossible to fix the conductive pins 65 to the base member 61.

Also, in the above-described illustrative embodiment, a case of formingthe supporting member 54 of copper is described. However, the presentinvention is not limited thereto. If a material has thermal conductivityhigher than that of the filament 66 or is thicker larger than thefilament 66, it is possible to appropriately modify the design.

Also, in the above-described illustrative embodiment, a configuration inwhich the emitter 52 is held in the cylindrical supporting member 54 isdescribed. However, the present invention is not limited thereto. Themethod of connecting the supporting member 54 and the emitter 52 can beappropriately modified.

What is claimed is:
 1. An emitter structure comprising: a pair ofconductive pins which are fixed to a base member; a filament which isconnected between the pair of conductive pins; and an emitter which isconnected to the filament and has a sharp tip; wherein a supportingmember is fixed to the base material, and the emitter is connected tothe supporting member.
 2. The emitter structure according to claim 1,wherein the supporting member is formed of a material having thermalconductivity higher than that of the filament.
 3. The emitter structureaccording to claim 1, wherein the supporting member is formed thickerthan the filament.
 4. The emitter structure according to claim 1,wherein the supporting member is formed in a cylindrical shape, andwherein the emitter is fixed while a base end portion of the emitter isinserted into the supporting member.
 5. A gas ion source comprising: theemitter structure according to claim 1; a gas source which is configuredto supply a gas to a vicinity of the emitter; a cooling unit configuredto cool the emitter; an extraction electrode which is disposed apartfrom the tip of the emitter; and an extraction power source unit whichis configured to apply an extraction voltage between the emitter and theextraction electrode to ionize the gas into gas ions at the tip of theemitter and extract the gas ions toward the extraction electrode.
 6. Afocused ion beam system comprising: the gas ion source according toclaim 5; and a beam optical system which is configured to convert theextracted gas ions into a focused ion beam and irradiate a sample withthe focused ion beam.